WALTHAM - Paul Pierce has waited too long, been on too many bad teams, watched too many seasons end well short of his goal. So even though it's obvious that, with the Eastern Conference finals tied at two wins apiece, the Celtics must play with renewed intensity and urgency tonight against the Detroit Pistons in Game 5, Pierce wasn't taking any chances.

Before the Celtics broke their huddle following a film session and light practice yesterday, Pierce was blunt with his teammates. He told them they needed to play as if it were the last game of their careers because none of them know whether they'll have this opportunity again.

"There are three games left in this series, and it has been six years since I've been to the Eastern Conference finals and it's my second time in 10 years," said Pierce. "This opportunity isn't guaranteed. A lot of players don't even make it that far, so it's a tremendous opportunity, and I want these guys to realize that."

While the Pistons are playing in their sixth straight Eastern Conference finals, that's a rarity. Getting this close to a ring doesn't happen that often for most NBA teams. The Celtics, who are coming off a 94-75 loss in Game 4 at the Palace of Auburn Hills, are either two wins away from advancing to the franchise's first NBA Fi nals since 1987 or two losses away from seeing a 66-win season go down as a disappointment. Tonight, they'll take a step in one direction or the other.

The Celtics can take solace in the fact that they haven't lost a Game 5 in this postseason, winning on their home court against both the Hawks and Cavaliers, and have yet to face a deficit in any of their playoff series. However, the Pistons have already scored one victory at the Garden (Game 2) and have four road wins in the playoffs, the most of any team.

Pierce's call to action might be a verbal response to the physical play of the Pistons in Game 4. Detroit harassed the Celtics into a 21-of-66 shooting night (31.8 percent), their worst of these playoffs. Coach Doc Rivers felt his players allowed Detroit to push them around and punish them with a strategy that was straight out of the Bad Boys era, or, as P.J. Brown put it, the "[Pat] Riley School of Hard Knocks," sending the Celtics to the line 39 times.

"Some of it was us. I thought half of it was them," said Rivers. "The number of free throws were nice, but they had the old Pat Riley rule: If you foul every single time, they're going to stop calling half of them. And that was pretty much true."

Rivers said his team needs to be mentally and physically tougher in Game 5.

"You can't allow them to deny you and push you off the block," said Rivers. "Half of our posts were halfway between the block and the 3-point line. That can't happen. Just go post and do it."

Playing a more determined brand of basketball starts with the Big Three, Pierce, Kevin Garnett, and Ray Allen. The trio seemed knocked off stride in Game 4, as they shot a combined 11 of 38 from the floor for a total of 43 points.

"It has to come from all of us, but definitely your All-Stars have to step up, meaning me, Kevin, and Ray," said Pierce, the designated Big Three spokesman yesterday. "We have to play better basketball, but it's a combination of all of us, from 1 all the way down to 12. There is definitely a lot of pressure, but hey, we're more than capable."

Pierce, Allen, and Garnett all know the sting of reaching a conference finals and failing. Pierce lost with the Celtics to the Nets in six games in 2002. Allen went to the 2001 Eastern finals with the Bucks, who dropped the seventh game to the 76ers. Garnett advanced to the Western finals in 2004 with the Timberwolves, but KG & Co. succumbed to the Lakers in six games.

None of the Big Three had been back to the conference finals until now.

Brown, who is in his 15th season, had to wait more than a decade to get a second chance at the Eastern Conference crown. In 1997, he was a fourth-year player on the Riley-led Heat, who fell to Michael Jordan and the Bulls in five games. He came out of retirement to join the Celtics and get a chance to play in games such as tonight's.

"You don't know if you're ever going to get a chance to get back," said Brown. "I know that with my 15 years, Paul knows that with his 10, but guys who are younger think you're going to be there forever.

"It's just hard. If I could implant my knowledge and experience, hey, it would be different, but I can't do that."

Pierce and Brown can't implant their knowledge to players like second-year point guard Rajon Rondo and rookie Glen "Big Baby" Davis, but they can impart it.

"What I try to tell guys is, 'Don't look at the scoreboard. Don't worry about us being up in the series. Just play every game, every moment, every possession like it's your last,' " said Brown. "That's the way it's got to be in playoff basketball."